The present invention relates generally to an optical see-through head-mounted display (OST-HMD) device, and more particularly, to ergonomically designed freeform optical systems for use as an optical viewing device in optical see-through HMDs with an eyeglass-form appearance and a wide see-through field of view (FOV).
Head-mounted displays (HMD) have long been proven invaluable for many applications, spanning the fields of scientific visualization, medicine and military training, engineering design and prototyping, tele-manipulation and tele-presence, and personal entertainment systems. In mixed and augmented reality systems, optical see-through HMDs are one of the basic approaches to combining computer-generated virtual scene with the views of a real-world scene. Typically through an optical combiner, an OST-HMD optically overlays computer-generated images onto the real-world view while maintaining a direct, minimally-degraded view of the real world. An OST-HMD has a great potential for creating a mobile display solution that offers much more attractive image quality and screen site than other popular mobile platforms such as smart phones and PDAs.
On the other hand, despite much significant advancement on HMD designs over the past decades, there exist many technical and usability barriers preventing the technology from being widely accepted for many demanding applications and daily usage. One of the major barriers with HMDs is the cumbersome, helmet-like form factor that prevents the acceptance of the technology for many demanding and emerging applications. Few of the existing optical design methods applied is capable of creating a truly portable, compact, and lightweight HMD design that is nonintrusive and can be considered as being eyeglass-style near-eye displays. Heavy weight contributes to fatigue and discomfort, and is considered a major hindrance of HMD-based applications. Additionally, the ability to provide a wide, minimally blocked or degraded see-through FOV is essential for performing daily tasks. In recent year, freeform surfaces have been introduced to HMD system designs [U.S. Pat. Nos. 5,699,194, 5,701,202, 5,706,136. D. Cheng, et al., “Design of an optical see-through head-mounted display with a low f-number and large field of view using a freeform prism, Applied Optics, 48(14), 2009.] aiming to reduce the system weight and create lightweight HMDs. However, there is still no solution available in today's market which meets both the ergonomic needs and performance needs. Our work aims to develop the solutions with eyeglass form factors and wide see-through FOV, while maintaining a superior performance.